Process and device for the biological treatment of organically polluted waste water and organic waste

ABSTRACT

A process and a device for biologically treating an organic waste mixture containing organically polluted waste water and solid components. The process and the device involve exposing the organic waste mixture to a first decomposition stage where the solid components and the waste water are separated from one another and where the solid components are decomposed under predominantly aerobic conditions. The waste water is then passed to a second decomposition stage where the waste water is decomposed under anoxic conditions. Thereafter, the waste water is passed to a third decomposition stage where the waste water is decomposed again under aerobic conditions thereby creating recirculation water. At least a portion of the recirculation water is returned from the third decomposition stage to the first decomposition stage for continuously recirculating water through and between respective decomposition stages.

FIELD OF THE INVENTION

The invention relates to a process and device for the biologicaltreatment of organically polluted waste water and organic waste. It isthe aim of such processes to decompose the organic material intolow-molecular, low-energy compounds while reducing their volume as muchas possible (mineralization), which can be discharged, for example intothe ground or the sewer system, without placing a noticeable burden onthe environment. The waste water from toilets, for example, essentiallycontains carbohydrates, C-polymers, proteins, amines, urea, ammonia andsalts.

While the carbohydrate-containing components can be decomposed underaerobic conditions into carbon dioxide and water by microorganisms, thereduced nitrogen compounds are decomposed essentially into water andnitrates by nitrogen-fixing bacteria. Accordingly, the liquid obtainedin the course of such aerobic decomposition processes containsconsiderable amounts of nitrate. Their introduction into rivers or lakesresults in a nitrate over-fertilization having undesired consequences,such as increased growth of algae. Since nitrate ions are only lightlyretained in the ground and accordingly can be easily washed out of theground layers near the surface by rain water, their escape from, forexample agricultural land, endangers the ground water.

Processes are known wherein an additional anaerobic decomposition stageis provided in order to convert at least a part of the nitrate intoinnocuous elementary nitrogen by means of nitrate-reducingmicroorganisms. A process is known from U.S. Pat. No. 4,210,528, whereinthe waste water from toilets, together with the solids containedtherein, is brought into a first anaerobic decomposition stage and issubsequently subjected to an aerobic treatment. In this process theliquid from the aerobic stage is filtered, passed over a bed ofactivated charcoal and used as the flushing water for the toilets. Inthis way the nitrate-containing water gets back into the anaerobicdecomposition stage and is available there to the nitrate-reducingbacteria as a provider of oxygen for their respiratory metabolism.

A disadvantage of the known process or the known device lies in that thecomponent of solids, which constitutes the main portion of the organicmaterial to be decomposed, is subsequently decomposed under anoxicconditions. Biological communities of organisms are described by theterm anoxic, in whose vicinity chemically fixed oxygen, for example inthe form of nitrate, is present, but no dissolved oxygen. Decompositionunder the mentioned conditions takes place by means of microorganismswhich satisfy their oxygen requirements by reduction of the nitrate.This process is generally identified as nitrate reduction. Thusdecomposition in the known processes depends on the presence of nitrate.To achieve complete decomposition, the portion of nitrogen compoundswould have to attain values which are not present in conventional andparticularly communal waste waters. The result is that, following theconsumption of the nitrogen compounds, sulfate reduction and anaerobicdecomposition processes begin. Besides the development of hydrogensulfide, there is the main disadvantage that the anoxic decompositionprocesses proceed considerably more slowly. Accordingly, extendedretention times or large reaction chambers are necessary to obtain asufficient decomposition rate. A further disadvantage of the knownprocess resides in that the return of nitrate-containing liquids fromthe anaerobic decomposition stage into the anoxic one is coupled to theuse of the toilets. An extended non-use of the toilet leads, on the onehand, to a lack of nitrate in the anoxic stage and an increase inaerobic decomposition processes whose end products are gases such asmethane, hydrogen sulfide and mercaptan. These gases enter theenvironment and contribute, among other things, to the destruction ofthe ozone layer, besides being strongly odiferous. A furtherdisadvantage of the known device lies in that it is necessary tocomminute the solid portion introduced into the anoxic decompositionstage in order to be able to achieve acceptable decomposition rates. Forthis purpose the known device provides a stirring device which isintermittently motor-driven and uses energy and is prone to malfunction.

SUMMARY OF THE INVENTION

Based on the above, it is the object of the invention to provide adevice and a process for the biological treatment of an organic wastemixture containing organically polluted waste, or solid components waterand organic waste, which device does not have the disadvantages of theprior art and is suited for mobile toilet installations.

This object is attained by a process according to which the solidportion of, for example toilet waste water or organic wet waste fromkitchens, etc., is separated and decomposed in a first decompositionstage under predominantly aerobic conditions. The liquid portion ispassed into an adjoining second decomposition stage in which anoxicconditions prevail. After passage through this decomposition stage, theliquid is finally passed into a third decomposition stage in whichaerobic condition prevail again. To increase the decomposition rates,biologically active substrate structures are present at least in thesecond and third stages which serve as growing surfaces for themicroorganisms. The liquid from the third stage is returned to the firststage for maintaining continuous recirculation.

An advantage of the process of the invention resides in that the solidswhich occur in relatively large amounts are mainly decomposedaerobically and therefore in an accelerated manner and practicallywithout the development of gases, such as methane and hydrogen sulfide,as is the case in connection with anaerobic decomposition processes. Thenitrate- and oxygen-containing liquid, which is continuouslyrecirculated from the third decomposition stage into the firstdecomposition stage, reaches the collection of solids at the firstdecomposition stage and moistens the collection of solids through layersthereof. By means of the above, aerobic metabolic processes in the areasof solid collection near the surface of the collection are aided bymeans of the oxygen content of the liquid. The liquid also penetrateslayers of the solid collection which are far from the surface of thecollection. Nitrate contained in the mixture is reduced to elementarynitrogen (denitrification). Metabolic processes generating methane andhydrogen sulfide are repressed in this manner. The liquid returned intothe first decomposition stage is enriched at that location with solubledecomposition products, such as sugar and fatty acids, and reaches thesecond decomposition stage, where denitrification takes place, i.e. thenitrate-reducing microorganisms or denitrifiers remove from the nitrateion the oxygen which is necessary for the "respiration" of carboncontaining compounds or C-compounds.

Finally, an aerobic decomposition of C-compounds into carbon dioxide andwater and the nitrification of nitrogen containing compounds orN-compounds, i.e. an oxidation into nitrate, takes place in the thirdstage. The nitrate created here is again decomposed to elementarynitrogen in the second decomposition stage because of the continuousrecirculation. As a final result, practically all of the nitrogen whichis bound in the form of organic compounds is converted into elementarygaseous nitrogen and removed from the decomposition circuit.

A further advantage of the process of the invention lies in that thedecomposition of the solids takes place in a separate stage with aconsiderable reduction of the volume or space necessary to effect suchdecomposition. The above is due solely to the fact that a portion of thewater content of the solids, which is up to 98% with plant materials,can evaporate. The evaporation of the water is further aided by theincrease of the temperature in the solid collection as a result of themetabolic processes of the microorganisms. This is not possible in theprocess according to the prior art, where the solid portion is suspendedin the liquid phase. A further reason for the large reduction in volumelies in that gaseous carbon dioxide and water are created as the endproducts of the anaerobic decomposition processes, where at least a partof the water also evaporates.

A further advantage of the process of the invention lies in the factthat foreign bodies which cannot be decomposed, for example those whichhave entered through the toilet, are already kept back in the firststage, where they practically do not interfere. In processes operatingwith solids suspensions, such foreign bodies can plug up filters andbiologically active substrate structures. In the extreme case this canresult in a standstill of the installation. Finally, a further advantageof the process of the invention lies in that the accumulation of sludgein the liquid phase, i.e. in the second and third decomposition stages,is considerably less as compared with the processes operating withsolids suspensions. Increased sludge formation can lead to plugged-upfilters and substrate structures and results in increased maintenanceand cleaning efforts.

In accordance with a further embodiment of the invention, themicroorganisms always have a sufficient amount of trace elementsavailable to them. Trace elements such as calcium, magnesium, cobalt,nickel and iron (micro-elements) are needed by the bacteria for buildingup endogenic substances, among other things. The above thereforecontributes to the creation of optimal conditions for themicroorganisms, which results in an increased rate of multiplication ofthe microorganism and decomposition effected thereby. On the other hand,the particles made of mineral matter or activated charcoal have a largeinterior surface because of their porosity, which interior surface canbe used by the microorganisms as an additional growing surface.Furthermore, activated charcoal particles have the advantages listedfurther down below.

According to yet another embodiment of the invention the activatedcharcoal bed is used as a "carbon reservoir", in that it has theproperty of adsorbing carbon compounds for allowing the denitrifierspresent in the anoxic decomposition stage to be able to always fall backon a carbon and energy reservoir. The above comes into play particularlyin case no fresh organic material has been supplied to the system for anextended period of time. A further advantage of the activated charcoalbed lies in its capacity to act as a "buffer", so to speak, for loadfluctuations. In case of large loads, a portion of the dissolved organiccompounds is retained adsorptively by the charcoal bed so that loadpeaks in the adjoining aerobic third decomposition stage are prevented.Two processes which compete for oxygen take place at the seconddecomposition stage, namely the oxidative decomposition of carboncompounds and nitrification of N-compounds. A large increase in theconcentration of decomposable carbon compounds naturally inhibits theparallel occurring nitrification. This would lead to a reduction of thenitrate concentration and in the end to the inhibition of thedenitrification at the second decomposition stage.

Finally, it is also advantageous that the activated charcoal bed cansimultaneously be used as the biological substrate structure, i.e. asthe growing medium, for the microorganisms.

According to a further embodiment of the invention, an entry ofadditional water into the system in the course of the biologicaltreatment of toilet waste water is prevented. On the one hand, the abovewould lead to a reduction in the retention time or would result in theneed to use correspondingly larger reaction chambers. On the other hand,the entry of additional water into the system during biologicaltreatment of the waste water would create the need to use valuabledrinking water for toilet flushing.

According to another embodiment of the invention the liquid is removedfrom the third decomposition stage and allocated for use as flushingwater for a toilet or water to be expelled to the environment in ahygienically unobjectionable condition. Particularly advantageousoptions for sterilization include the use of UV treatment, which is veryeffective, requires a small amount of energy, is easy to maintain and isenvironmentally friendly. However, processes such as pasteurization oranodic oxidation can also be employed.

Moreover, filtration and sterilization can be achieved by means of crossflow filtration. This process is practically maintenance-free, incontrast to conventional filter processes where the filters must alwaysbe cleaned or replaced. Depending on the type of diaphragm filter used,it is possible to achieve micro- or ultra-filtration. In the latter caseit is possible to even filter the smallest microorganisms, such asviruses, out of the liquid used for flushing the toilet or which ispassed on to the environment.

Since activated charcoal is a hydrophobic adsorbent, mainly non-polarcompounds or compounds with hydrophobic groups are adsorbed into thecharcoal, such as fats, fatty acids and oils from fecal matter andkitchen refuse. These compounds are therefore concentrated on thesurface of the activated charcoal, and therefore result in the formationof a flora which is particularly advantageous for the decomposition ofthe compounds. The result is a more effective decomposition of thecompounds. In contrast to toilet waste water and organic waste, communalwaste water contains appreciable amounts of relatively hard-to-decomposeactive laundry substances and preservation agents, and, in addition,tensides and substances such as chlorinated aromatics, and formaldehyde,aromatics, benzoic and sorbic acid. These compounds are also preferablyadsorbed by activated charcoal. A decomposition chamber can be providedin accordance with another embodiment of the invention by interposing afurther aerobic compartment with an activated charcoal bed between thesecond, anoxic, and the third, aerobic compartment in which a biologicalcommunity of organisms can form which specializes in the decompositionof the mentioned compounds. As mentioned above, the adsorption ofcompounds by activated charcoal causes a concentration of thehard-to-decompose compounds and thus an increase in the effectiveness ofdecomposition. A further advantage of the mentioned steps rests in thatthe retention time, in the compartment, of the absorbed compounds isincreased because of the adsorption. The above in turn has a positiveeffect on the settlement and increase of specialized microorganisms. Thementioned compounds are retained and decomposed in the interposedcompartment where they do not, or do only to a small extent, get intothe adjacent aerobic compartment. The microorganisms which have settledin the interposed compartment are therefore protected from the tensideand hydrocarbon load of the waste water. Therefore two decompositionchambers with different floras are produced by means of theinterposition of a further compartment as noted above, where thedifficult-to-decompose load of dirt in the waste water is kept back inthe interposed compartment and is decomposed by specializedmicroorganisms.

The object of the invention is further attained by a device suitable forexecuting the process in accordance with the invention. According to oneembodiment of the invention, the different decomposition compartmentsare arranged one above the other. The above arrangement is particularlyadvantageous if the device of the invention is to be placed ininstallations with limited usable space, for example railroad cars ormobile homes.

According to another embodiment of the invention, a biologically activesubstrate structure comprising a plastic sintered material can bedisposed in the second compartment, and can further be produced simplyand cost-effectively. The material is also very usable for sintering-inporous particles made of mineral materials and/or activated charcoal, ina simple manner. The advantages of such an arrangement have already beendescribed above.

According to yet another embodiment of the invention, the secondcompartment is connected with the third compartment disposed below it byan overflow pipe disposed in the second compartment and extending overalmost its entire height. In the above arrangement, the secondcompartment and the substrate structure and activated charcoal bedlocated therein are always covered with liquid. By means of the above,it is possible to always maintain strict anoxic conditions.

According to a further embodiment of the invention, a filter basket forkeeping back the solid components is disposed in the first compartment.The filter basket may comprise woven wire or plastic sintered material.In addition, porous particles of a mineral material and/or activatedcharcoal may be embedded in the plastic sintered material. As alreadymentioned above, the latter embodiment in particular has the advantagethat the porous particles of a mineral material embedded in the filterconstitute a depot for trace elements which can be accessed by themicroorganisms which decompose the solids portion. Furthermore, theembedded porous particles have the advantage of having a large interiorsurface and can therefore serve, in addition to the plastic sinteredparticles, to immobilize microorganisms. The same applies to theactivated charcoal particles embedded in the sintered material.

In accordance another embodiment of the invention, means for injectingair are provided in the third compartment in order to maintain asufficiently high oxygen content in the liquid.

In accordance with yet another embodiment of the invention the airescaping from the liquid in the third compartment is advantageouslyemployed for assisting the aerobic solids decomposition in the firstcompartment. This step is particularly effective if the air can bedistributed as evenly as possible within the collection of the solids.

BRIEF DESCRIPTION OF THE DRAWINGS

The invention will now be explained in detail by means of exemplaryembodiments represented in the attached drawings where:

FIG. 1 is a cross sectional schematic view of an embodiment of thedevice of the invention;

FIG. 2 is a cross sectional schematic view of a further embodiment ofthe device of the invention;

FIG. 3 is a partial cross sectional schematic view of an embodiment ofthe invention showing an advantageous design of the biologically activesubstrate structure in the third compartment;

FIG. 4 is a cross sectional view of an exemplary schematic embodiment ofthe invention, showing an integrated toilet;

FIG. 5 is a cross sectional schematic view of an exemplary embodiment ofthe invention, showing an integrated toilet and cross-flow filtration;

FIG. 6, is a view corresponding to FIG. 5, showing an additional aerobiccompartment;

FIGS. 7 and 8, are views corresponding to FIG. 6, showing alternaterelative dispositions of the compartments.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

As can be seen from FIG. 1, the device in accordance with the inventioncontains altogether three stacked compartments (1, 2, 3) which togethercomprise a bioreactor 4. The first compartment, compartment 1, disposedat the top of the bioreactor is connected to the outside air and isdesigned for aerobic decomposition. The second compartment, compartment2, disposed below compartment 1 is used for anoxic decomposition, andthe lowest compartment 3 which is the third compartment finally is againused for aerobic decomposition. A horizontally extending separating wall5 is disposed between the compartments 1 and 2, and is permeable toliquids. A filter basket 6, open at the top, is disposed in thecompartment 1 and is used for separating the solid components from thewaste water supplied to the device. The solid components are depositedin the filter basket 6 in the form of a filter cake 7. The filter basket6 has vertical lateral walls 8 and a horizontally extending bottom 9. Inthe simplest embodiment, the lateral walls 8 and the bottom 9 could bemade of wire mesh. But at least the bottom 9 can also be made of aplastic sintered material. Polyethylene, for example, can be used as theplastic. Sintered material of this type is obtained by sintering theplastic particles together. In the process, a material interspersed withhollow spaces or pores is created. Such materials are used in othertechnical fields, for example, as air filters. A further embodimentoption for the filter basket 6 consists in placing a layer of thesintered material on the wire mesh bottom 9 of the filter basket 6.Finally, it is also conceivable to make the entire filter basket 6 of aplastic sintered material. Particles of a mineral material and/oractivated charcoal particles can be embedded in the plastic sinteredmaterial. Such particles are porous and provide additional growingsurfaces for microorganisms available. Furthermore, the mineral materialparticles function as depositories for trace elements.

It is also conceivable to use two filter baskets instead of one and tocharge the baskets successively. The above could also be achieved bymeans of a filter basket divided into two halves. Finally, it is alsopossible to dispose the filter basket replaceably in the compartment 1.The above would have the advantage that a filter basket could be simplyexchanged for a cleaned filter basket during regularly scheduledcleaning of the device.

The compartment 2, in which anoxic conditions prevail, is disposed belowthe aerobic compartment 1. A bed 11 of activated charcoal grains isdisposed in the lower part 10 of the compartment 2 and extends overpractically its entire cross-sectional surface in a horizontal plane toform a biologically active substrate structure. A layer of abiologically active substrate structure 12, essentially consisting of apolyethylene sintered material, also extending over practically theentire cross-sectional surface, in a horizontal plane, of thecompartment and essentially extending parallel with the bottom 9 of thefilter basket, is disposed in the remainder of the space of thecompartment 2 above the activated charcoal bed 11. Particles of porousmineral materials, such as light expanded clay aggregate, slag or tufa,are embedded in this sintered material. It is also possible to embedinto the sintered material activated charcoal particles. The functioningof this filter and of the particles therein embedded will be describedfurther below.

The compartment 2 is separated from the compartment 3 disposed below itby means of a gas- and liquid-proof separating wall 13. The connectionbetween the two compartments is assured by an overflow pipe 14 disposedin the compartment 2 and connected with the compartment 3. This overflowpipe 14 essentially extends over the entire height of the compartment 2,so that the activated charcoal bed 11 and the substrate structure 12contained therein are covered with dammed-up liquid. Biologically activesubstrate structures 15 are also disposed in the compartment 3. Theseare embodied in the form of walls extending vertically, disposedparallel in respect to each other and essentially extending over theentire width of the compartment 3. The vertical extension of thesubstrate structures 15 is slightly less than the height of thecompartment 3. A space is therefore present between the upper end facesof the substrate structures 15 and the separating wall 13, which spaceallows a flow of liquid. The substrate structures 15 are also made of apolyethylene sintered material into which mineral material and/oractivated charcoal is embedded. Ventilating means 17 are disposed at thebottom 16 of the compartment 3. These can be embodied in the form ofpipes, for example, which are disposed between the substrate structures15 and whose surfaces are perforated. Air blown into the pipes exitsthrough the perforations of the pipes and is partially dissolved in theliquid. The excess air, collecting below the separating wall 13, can beremoved through an opening (not shown) in the compartment 3.

A drain opening 19 is provided in the lower area of the lateral wall 18of the compartment 3 adjoining the bottom 16 and is connected with arecirculating line 20. The recirculating line 20 is guided toward thetop into the compartment 1 and terminates there. A recirculating pump 21is disposed in the recirculating line 20 for maintaining a recirculatingflow of liquid. An outlet line 22 branches off the recirculating lines20, by means of which it is possible to drain liquid from thecompartment 3 when a defined filling level has been reached. For thispurpose the outlet line 22 has a valve 23 which is triggered via afilling level sensor (not shown) in the compartment 3. In addition, asanitizing and filtering unit 24 is disposed between the valve 23 andthe outlet line 22.

The process in accordance with the invention will now be described bymeans of the exemplary embodiment illustrated in FIG. 1:

The waste water coming from one or several toilets, for example, issupplied through an inlet line (not shown) to the compartment 1. Thesolids portion of the waste water (fecal matter, toilet paper, etc.) isretained in the filter basket 6 disposed therein, because of which acollection of solids builds up in the manner of a filter cake 7 withtime. The liquid running out of the compartment 1 first reaches thecompartment 2 and then, via the run-off pipe 14, the compartment 3. Thecompartment 1 is connected with the environment so that the entry ofoxygen from the air for maintaining the aerobic conditions is assured.As will be shown further down below, a forced ventilation of the filtercake 7 can take place to assist aerobic decomposition, in particular incase of increased amounts of solids.

Aerobic conditions prevail in the areas of the filter cake 7 close tothe surface thereof or in the areas located in the vicinity of theforced ventilation means (air distributor 26 in FIG. 2)(to be describedfurther below). Essentially, an oxidative decomposition of organiccarbon and nitrogen compounds (carbohydrates, fats, proteins) takesplace here. Both processes can be shown by way of example by means ofthe following simplified empirical formula: ##STR1##

The empirical formulas IV and V represent the processes occurring duringthe so-called nitrification stage. The first reaction step IV isperformed for example by nitrosomonas and the second in accordance withV, for example by nitrobacters.

Anaerobic and anoxic decomposition processes take place in lower layersnot provided with oxygen, which can be represented in a simplifiedmanner by means of an example of glucose in approximately this way:##STR2##

The nitrate converted by denitrification (VIII) into nitrogen in theanaerobic zones of the filter cake comes mainly from the liquid from thecompartment 3, which was supplied to the compartment 1 through therecirculating line 20, and partially from the nitrification in theaerobic zones of the filter cake 7. Because of the presence of nitrate,the methane formation in accordance with VI is forced back in favor ofthe denitrification.

Anoxic conditions prevail in compartment 2. The liquid in thiscompartment predominantly contains nitrate and organic C-compounds whichpartially stem from the toilet waste water supplied, and partially fromthe decomposition process taking place in the solids compartment 1. Thedecomposition of nitrate/nitrite to elementary nitrogen(denitrification) takes place under the prevalent anoxic conditions. Thegaseous nitrogen is conducted to the outside through an opening (notshown) in the compartment 2. In the course of denitrification, alsocalled "nitrate respiration" because of its parallelism with oxygenrespiration, the nitrate ion is used as the oxygen supplier or as aterminal hydrogen acceptor. The decomposition processes operating during"respiration" can be represented in a simplified manner in approximatelythe following manner: ##STR3##

In this compartment the methane formation is also extremely low andpractically negligible.

The activated charcoal bed 11 disposed in the compartment 2 and thesubstrate structure 12 located above it have several functions. For one,they are used as a growth material for microorganisms, i.e. after sometime in use, their exterior and at least a part of their interiorsurface is covered by a growth of bacteria. Furthermore, the activatedcharcoal bed 11 functions as a "carbon buffer". Organic C decompositionproducts released from the filter cake 7 or soluble organic C-compoundsand dyestuffs from fecal matter contained in the waste water fed to thecharcoal bed, or aromatic and aliphatic hydrocarbons are kept back byadsorption by the activated charcoal bed 11. Activated charcoal has theproperty of adsorbing non-polar or hydrophobic compounds or those withhydrophobic groups, and is thus "loaded up" with these compounds. Twoeffects are attained by virtue of the above. For one, a sharp increasein the concentration of the C-compounds mentioned above is prevented inthe compartment 3 in the case of load peaks, i. e. of increased amountsof supplied waste water or heavily contaminated waste water. As will beshown, two different reactions competing for oxygen take place in thiscompartment, namely the oxidative decomposition of organic carboncompounds and, parallel thereto, the nitrification taking placefollowing the mineralization of organic nitrogen compounds. Naturallythe first mentioned reaction would preferably take place with anincreasing concentration of the organic carbon compounds, whilenitrification would be inhibited correspondingly. A second effect of the"buffer effect" lies in that in case of a lack of waste water suppliedto the compartment 1 over a longer period of time, the depletion ofcarbon-containing organic compounds is compensated. Thus, thedenitrification could fall back on the carbon compounds adsorbed intothe activated charcoal and assure an optimal conversion of nitrate intoelementary nitrogen.

Aerobic conditions again prevail in the third compartment 3 and aremaintained by the injection of air therein by ventilating means 17.Similar to the aerobic regions in the filter cake 7, two differentdecomposition processes take place in the third compartment. In theinlet area, i.e. in the area in the vicinity of the termination of theoverflow pipe 14, the oxidative decomposition of the remainder oforganic compounds still contained in the liquid preferably takes place.In the areas further away from the overflow pipe 14, however,nitrification is preponderant. The substrate structures 15 of thecompartment 3 are used as a growing medium for microorganisms.

Because of their interior surfaces, the mineral material and/oractivated charcoal particles embedded in the substrate structures 12, 15or in the polyethylene sintered material in general cause an increase inthe growth surfaces for microorganisms. Furthermore, the mineralmaterial particles are used for supplying the microorganisms with traceelements.

An exemplary embodiment is represented in FIG. 2 in which the air fed tothe compartment 3 is supplied via a collecting line 25 to an airdistributor 26 disposed inside the filter basket 6. As shownschematically by way of example in FIG. 2, this air distributor 26 cancontain perforated pipes 27 disposed at a distance from each other inthe filter basket 6 and extending in the vertical direction. In this wayit is possible to decompose an increased portion of the filter cake 7aerobically.

An embodiment of a device in accordance with the invention isillustrated in FIG. 3, wherein each second substrate structure has aflow-through opening 29 in its lower area and wherein the substratestructure 15 located between two such substrate structures has a reducedheight. The liquid flowing from the mouth of the overflow pipe 14 to theoutflow opening is therefore forced to take the path indicated by thearrows 48. The advantage of this embodiment lies in that thebiologically active contact surface 28 provided by the substratestructures 15 as a whole is utilized more effectively.

A device in accordance with the invention with a toilet connectedtherewith is represented in FIG. 4. This device is particularly suitedfor toilet installations in vehicles, such as travel trailers orrailroad cars. In this embodiment the compartment 1 is connected via asupply line 31 with a toilet 30. The flushing liquid for the toilet istaken from the compartment 3 and supplied via a flushing water line 32to a reservoir 33, from which it can be taken as needed for flushing thetoilet 30.

On the flushing water side, the toilet 30 is connected via a line 49with the reservoir 33. A valve 46 is disposed in the line 49 and can beoperated manually or by foot, for example.

A sanitizing device 34 and a filter 35 are placed upstream of thereservoir 33. By means of the filter 35 it is possible to filter outfine solids particles from the liquid drawn from the compartment 3. Itis also conceivable to provide this filter unit with an additionalactivated charcoal filter by means of which it would be possible, forexample, to absorb dyestuffs dissolved in the liquid. To sterilize theliquid in the sanitizing device 34, it is possible to proceed indifferent ways. UV radiation has proven to be particularly advantageous,since it operates dependably and in addition has a very low energyconsumption. A pump 36 for conveying the liquid from the compartment 3to the reservoir 33 is disposed in the flushing water line 32. A filllevel regulator (not shown) is disposed in the reservoir 33, whichswitches the pump on at a minimum fill level and switches it off at amaximum fill level. In this exemplary embodiment, the recirculation ofthe liquid inside the bioreactor 4 has been resolved in the same manneras with the exemplary embodiments corresponding to FIGS. 1 and 2. Theremoval of liquid from the system takes place via an outlet line 22branching off the flushing water line 32 downstream of the sanitizingunit 34. In this case the valve 23' is closed, but the valve 23 isopened.

An exemplary embodiment with an integrated cross flow filterinstallation is illustrated in FIG. 5. The cross flow filterinstallation contains a cross flow filter 37 as the essential component.The latter has an inlet 38 for the liquid from the compartment 3 to befiltered, a permeate outlet 39 and a residue outlet 40. The inlet 38 isconnected via a main flow line 41 with the drain opening 19 of theaerobic compartment 3. The permeate outlet 39 is connected via apermeate line 42 with the reservoir 33. Finally, the residue outlet 40is connected via a residue line 43 with the aerobic compartment 3. Avalve 45 is disposed in the residue line 43. The cross flow filterinstallation operates as follows: the liquid from the aerobiccompartment 3 is transported by means of a main flow pump 44 to thecross flow filter 37. The liquid filtered in the cross flow filter 37,the permeate, flows via the permeate line 42 to the reservoir 33. Theresidue, however, flows via the residue line 43 and the opened valve 45back to the compartment 3. A recirculating line 47, which terminatesfrom above in the compartment 1, branches off in the direction of thepermeate flow upstream of the valve 45. The cross section of therecirculating line 47 is designed in such a way that, when the crossflow installation is operating, a recirculating flow adapted to therespective design of the bioreactor 4 is assured.

When reaching a defined maximum liquid level in the reservoir 33, thevalve 45 is closed by a suitable control device (not shown) and the mainflow pump 44 is turned off. In order to assure a continuousrecirculation of the liquid in the bioreactor 4 even in this operationalstate, a recirculating pump 21 is disposed in a parallel circuit withthe main flow pump 44. The former is put into operation when the maximumfill level in the reservoir 33 has been reached. A return of the liquidfrom the aerobic compartment 3 into the first aerobic compartment 1takes place in this way via the main flow line 41, the residue line 43and the recirculating line 47. It is of course possible to employ atwo-stage or continuously controllable pump in place of two separatepumps 44, 21 with different conveying outputs.

In a device with, for example, a 400 liter bioreactor, the liquid flowsrepresented in the following table occur:

                  TABLE 1                                                         ______________________________________                                        Main flow            apprx. 1500 1/h                                          Permeate flow        20-30 1/h                                                Residue flow         apprx. 1460 1/h                                          Recirculating flow   15 1/h                                                   ______________________________________                                    

The removal of liquid from the bioreactor is assured in this embodimentby means of an outlet line 22, closed by a valve 23, which is attachedto the reservoir 33 below the maximum fill level. Upon reaching themaximum fill level in the compartment 3 as well as in the reservoir 33,the recirculating pump 21 is shut off and the main flow pump 44 turnedon by means of a suitable control device (not shown), and the valve 45is opened. The permeate flow is conducted via the permeate line 42 intothe reservoir 33 and removed to the outside via the valve 23 which isalso opened at this time.

An exemplary embodiment is represented in FIG. 6, wherein the bioreactor4 is composed of a total of four compartments. A compartment 2b in whichaerobic conditions prevail is disposed below the compartment 1.Ventilating means 17 embodied as perforated pipes through which air isblown are disposed in an area close to the bottom of compartment 2b formaintaining these conditions. An activated charcoal bed 11 is disposedas the growth material for microorganisms and extends practically overthe entire cross-sectional surface of the compartment 2b in a horizontalplane. However, in the vertical direction it only fills the center areaof the compartment 2b, so that spaces 51 and, 52, free of activatedcharcoal, are respectively formed between the activated charcoal and theseparating wall 5 with the compartment 1, and the separating wall 50 tothe compartment 2a which adjoins the lower portion of the activatedcharcoal. The ventilating means 17 are located in the space 52.

A compartment 2a adjoins the bottom of the compartment 2b and alsocontains an activated charcoal bed 11 and is separated from thecompartment 2b by the separating wall 50. So, while this separating walllets liquid and gas through, the separating wall 5 between thecompartment 1 and the compartment 2b is sealed against gas and liquids.Anoxic conditions prevail in the compartment 2a and aerobic conditionsin the compartment 2b.

The compartment 2a is connected with the compartment 1 via a connectingpipe 53, whose upper end passes through the separating wall 5 and whoselower end terminates in the area 54 close to the bottom of thecompartment 2. Compartment 2a contains an activated charcoal bed andextends over the entire cross-sectional surface of the compartment 2a ina horizontal plane. The two compartments 2a and 2b are connected witheach other via the liquid- and gas-permeable separating wall 50.

The compartment 2b is connected with the compartment 3 by means of anoverflow pipe 14, whose lower end terminates in the upper part of thecompartment 3 and whose upper end terminates in the space 51 locatedbetween the activated charcoal bed 11 and the separating wall 5.

The mode of operation of the device illustrated in FIG. 6 is as follows:the liquid flowing out of the filter basket 6 reaches the area 54 of thecompartment 2a via the connecting pipe 53, and from there thecompartment 2b via the separating wall 50. The compartments 2a and 2band the activated charcoal beds 11 therein are covered with dammed-upliquid. Finally, from the compartment 2b the liquid reaches thecompartment 3 via the overflow pipe 14.

The decomposition of organic compounds with simultaneous nitratereduction (denitrification) takes place in the compartment 2a, the sameas in compartment 2 of the above described exemplary embodiments, but anaerobic decomposition in compartment 2b. The advantage of the additionalcompartment 2b has already been described above.

In the device in accordance with FIG. 6, in the compartment 2a the flowis directed from below against the activated charcoal bed 11. Theadvantage of this type of flow which, incidentally can also be used inthe above described exemplary embodiments, lies in that the solids andsludge particles carried along with the liquid can be deposited in thearea 54 below the activated charcoal bed 11. By means of an outlet line64 disposed in this area it is possible to easily remove the sludgeaccumulations from there by opening the valve 65. If required, this canalso take place independently of regularly scheduled maintenance work.With a flow from the top onto the activated charcoal bed 11, the solidsor sludge particles can be deposited on top of the activated charcoalbed 11 and seal it off in the manner of a filter cake.

A filter layer 55 of a decomposable material is disposed on the bottom 9of the filter basket 6. Pressed straw pieces have been proven to beparticularly advantageous. Such a filter layer is progressively loosenedup by biological decomposition while forming new penetration channels,so that the sealing of already present penetration channels by solidparticles is compensated in this manner. A layer of pressed straw pieceswith a height of approximately 2 cm and having the following parametershas been shown to be advantageous:

    ______________________________________                                        Bed volume, dry:     500 g/l                                                  Water absorption:    2 1/1 or 4 1/kg                                          Density, swelled:    apprx. 1 kg/l                                            Fiber length, swelled:                                                                             1 to 5 mm                                                ______________________________________                                    

FIGS. 7 and 8 show exemplary embodiments of a device in accordance withthe invention with a different arrangement of the compartments 1, 2a, 2band 3. While the compartments 2a and 2b continue to be arranged aboveeach other as in the exemplary embodiment corresponding to FIG. 6, thecompartment 3 is disposed laterally thereof. The compartments 2a, 2b and3 are disposed in a common container 56 and are separated from eachother by a baffle plate 57.

The compartment 1 is placed in a separate container 58, which isdisposed laterally on the container 56 and in such a way that its bottom66 is located above the liquid level 59 in the container 56. Thecompartment 1 is connected with the compartment 2a via a connecting pipe53. The latter branches off toward the bottom of container 56 from thecontainer 58 and terminates below the activated charcoal bed 11 of thecompartment 2a. In this exemplary embodiment the flow is also directedfrom below against the activated charcoal bed 11 in an advantageousmanner. The height of the baffle plate 57 is less than the height of thewater column in the container 56.

In the exemplary embodiment in accordance with FIG. 8, the compartments2a and 2b are also disposed side-by-side in the container 56. The twocompartments are separated from each other by two walls 60, 61, whichare disposed parallel and at a distance from each other. The height ofthe wall 60 is less than the liquid column in the container 56, but theheight of the wall 61 is greater. The wall 61 has at least one opening62 at its end near the bottom. In this way the two walls 61 and 62 forma conduit connecting the two compartments 2a and 2b, through which theliquid flows from the compartment in the direction of the arrow 63.

The advantage of the arrangements in accordance with FIG. 7 and FIG. 8mainly consists in that the individual compartments are easilyaccessible from above for maintenance and cleaning work. They areadvantageously employed in all cases where little installed height isavailable or where installation in the ground is necessary.Accessibility from above is a considerable advantage in the last case inparticular.

Two sample layouts are shown in the following Tables 2 and 3. In eachcase an input which was burdened with 6100 mg/l chemical oxygen demandor COD, and a total nitrogen content of 1500 mg/l was used as the basis.With a retention time of three days, a reduction of the COD value byapproximately 95% and of the total nitrogen content by approximately 88%was achieved in both cases.

                  TABLE 2                                                         ______________________________________                                                      COD [mg/l]                                                                              Total N [mg/l]                                        ______________________________________                                        Input           6100        1500                                              Output           300         180                                              Volume loading  1800 mg/l d*                                                                               660 mg/l d                                       Recirculation rate                                                                            5/d                                                           Reactor volume  400 l                                                         Solids compartment                                                                            100 l                                                         Anoxic compartment                                                                            100 l                                                         Aerobic compartment                                                                           200 l                                                         Retention time   3 d                                                          ______________________________________                                    

                  TABLE 3                                                         ______________________________________                                                      COD [mg/l]                                                                              Total N [mg/l]                                        ______________________________________                                        Input           6100        1500                                              Output           300         180                                              Volume loading  1933 mg/l d*                                                                               660 mg/l d                                       Recirculation rate                                                                             5/d                                                          Reactor volume  40 l                                                          Solids compartment                                                                            22 l                                                          Anoxic compartment                                                                             6 l                                                          Aerobic compartment                                                                           12 l                                                          Retention time   3 d                                                          ______________________________________                                         *This value relates to the total content of dissolved and solid               oxygenconsuming substances; the latter are mainly decomposed in the solid     compartment.                                                             

A device in accordance with the invention with a layout corresponding toTable 2 is suitable for use in a railroad car, for example. The outputshows COD as well as nitrogen values which permit the dispersal orexpelling of the liquid directly into the ground, preferably duringtravel. The compartment 1 which retains the solids and decomposes thempreferably aerobically is laid out in such a way that the maintenanceintervals for emptying and cleaning are several months. In contrast tothis, the reservoir of conventional toilet installations must be emptiedat intervals of several days.

The device in accordance with the invention is also suited for othervehicles, such as mobile homes, aircraft and ships. Also conceivable isthe employment in buildings to which sewers cannot be connected, as inthe case of summer houses or weekend houses. It is also conceivable toemploy the device of the invention in mobile toilet installations whichcan be used at large construction sites or with outdoor events, forexample. In the same way it is conceivable to connect the device inaccordance with the invention to one or several vacuum toilets.

We claim:
 1. A process for biologically treating an organic wastemixture containing organically polluted waste water and solidcomponents, the process comprising the steps of:exposing the organicwaste mixture to a first decomposition stage, the step of exposingincluding the steps of:separating the solid components and the wastewater from one another; and decomposing the solid components underpredominantly aerobic conditions; passing the waste water from the firstdecomposition stage to a second decomposition stage; decomposing thewaste water at the second decomposition stage under anoxic conditions;passing the waste water from the second decomposition stage to a thirddecomposition stage; decomposing the waste water at the thirddecomposition stage under aerobic conditions thereby creatingrecirculation water; returning at least a portion of the recirculationwater from the third decomposition stage to the first decompositionstage for continuously recirculating water through and betweenrespective ones of the first decomposition stage, the seconddecomposition stage and the third decomposition stage.
 2. The processaccording to claim 1, wherein at least the steps of decomposing thewaste water at the second decomposition stage and decomposing the wastewater at the third decomposition stage include the step of utilizingbiologically active substrate structures.
 3. The process according toclaim 2, wherein at least the step of decomposing the waste water at thesecond decomposition stage includes the step of utilizing a substratestructure having embedded therein at least one of porous mineralmaterial particles and activated charcoal particles.
 4. The processaccording to claim 3, wherein the step of decomposing the waste water atthe second decomposition stage further includes the step of utilizing anactivated charcoal bed.
 5. The process according to claim 2, wherein thestep of decomposing the waste water at the second decomposition stageincludes the step of utilizing an activated charcoal bed.
 6. The processaccording to claim 1, further including the step of allocating a portionof the recirculation water to serve as at least one of flushing waterfor a toilet and water to be expelled from the device.
 7. The processaccording to claim 6, further including the step of filtering andsterilizing the recirculation water before the recirculation water is atleast one of used as flushing water for the toilet and expelled.
 8. Theprocess according to claim 7, wherein the step of sterilizing includesthe step of exposing the recirculation water to one of UV radiation,pasteurization and anodic oxidation.
 9. The process according to claim7, wherein the step of filtering includes the step of subjecting therecirculation water to at least one of micro-filtration and cross flowfiltration.
 10. The process according to claim 1, wherein the step ofpassing the waste water from the second decomposition stage to the thirddecomposition stage includes the step of passing the waste water fromthe second decomposition stage to a fourth decomposition stageinterposed between the second decomposition stage and the thirddecomposition stage, the process further including the step ofdecomposing the waste water at the fourth decomposition stage underaerobic conditions.
 11. The process according to claim 10, wherein atleast the steps of decomposing the waste water at the seconddecomposition stage, decomposing the waste water at the thirddecomposition stage and decomposing the waste water at the fourthdecomposition stage include the step of utilizing biologically activesubstrate structures.
 12. The process according to claim 11, wherein thestep of utilizing biologically active substrate structures includes thestep of using an activated charcoal bed.
 13. The process according toclaim 11, wherein at least the step of decomposing the waste water atthe second decomposition stage includes the step of utilizing asubstrate structure having embedded therein at least one of porousmineral material particles and activated charcoal particles.
 14. Adevice for biologically treating an organic waste mixture containingorganically polluted waste water and solid components, the devicecomprising:a first compartment for separating the solid components andthe waste water from one another, and for decomposing the solidcomponents under predominantly aerobic conditions; a second compartmentin flow communication with the first compartment for receiving the wastewater therefrom, the second compartment being effective for decomposingthe waste water under anoxic conditions and including a first set ofbiologically active substrate structures disposed therein; a thirdcompartment in flow communication with the second compartment forreceiving the waste water therefrom, the third compartment beingeffective for decomposing the waste water under aerobic conditions andincluding a second set of biologically active substrate structuresdisposed therein; and means operatively connected to the firstcompartment and the third compartment for returning at least a portionof the recirculation water from the third compartment to the firstcompartment.
 15. The device according to claim 14, wherein the firstcompartment, second compartment and third compartment are arranged in astack such that one of the compartments forms a top compartment, anotherof the compartments forms a middle compartment, and a last one of thecompartments forms a bottom compartment.
 16. The device according toclaim 15, wherein the second compartment is disposed above the thirdcompartment and includes an overflow pipe disposed therein, the overflowpipe extending over almost an entire height of the second compartmentand effecting flow communication between the second compartment and thethird compartment.
 17. The device according to claim 14, wherein thefirst set of biologically active substrate structures include a plasticsintered material.
 18. The device according to claim 17, wherein theplastic sintered material has embedded therein at least one of porousmineral material particles and activated charcoal particles.
 19. Thedevice according to claim 14, wherein the first set of biologicallyactive substrate structures includes an activated charcoal bed.
 20. Thedevice according to claim 14, wherein the first set of biologicallyactive substrate structures include:a plastic sintered material havingembedded therein at least one of porous mineral material particles andactivated charcoal particles; and an activated charcoal bed.
 21. Thedevice according to claim 20, wherein the plastic sintered material isdisposed above the charcoal bed.
 22. The device according to claim 14,wherein the first compartment includes a filter basket disposed thereinfor retaining the solid components.
 23. The device according to claim22, wherein the filter basket is made of woven wire.
 24. The deviceaccording to claim 22, wherein the filter basket is made of plasticsintered material.
 25. The device according to claim 24, wherein theplastic sintered material has embedded therein at least one of porousmineral material particles and activated charcoal particles.
 26. Thedevice according to claim 14, wherein the third compartment includesmeans for injecting air into the waste water contained therein.
 27. Thedevice according to claim 26, wherein the first compartment includes afilter basket disposed therein for retaining the solid components, thedevice further including means for transferring air escaping from wastewater contained in the third compartment to the first compartment fordistributing the air therein within the filter basket.
 28. The deviceaccording to claim 14, wherein the second set of biologically activesubstrate structures essentially comprise a plastic sintered materialhaving embedded therein at least one of porous mineral materialparticles and activated charcoal particles.
 29. The device according toclaim 14, wherein the means for returning includes means forcontinuously recirculating water through and between respective ones ofthe first compartment, the second compartment and the third compartment.30. The device according to claim 14, further including means forallocating a portion of the recirculation water to serve as at least oneof flushing water for a toilet and water to be expelled from the device.31. The device according to claim 30, further including a filtering andsterilizing unit for filtering and sterilizing the recirculation waterbefore the recirculation water is at least one of used as flushing waterfor the toilet and expelled from the device.
 32. The device according toclaim 31, wherein the filtering and sterilizing unit comprises a crossflow filtration device.
 33. The device according to claim 31, whereinthe filtering and sterilizing unit includes means for exposing therecirculation water to one of UV radiation, pasteurization and anodicoxidation.
 34. The device according to claim 15, further including afourth compartment having an inlet in flow communication with the secondcompartment for receiving waste water therefrom, and an outlet in flowcommunication with the third compartment for supplying waste waterthereto, the fourth compartment being effective for decomposing wastewater under aerobic conditions.
 35. The device according to claim 34,wherein the fourth compartment includes means for injecting air thereinand is disposed above the second compartment.
 36. The device accordingto claim 34, wherein the fourth compartment includes a third set ofbiologically active substrate structures disposed therein comprising anactivated charcoal bed.